IN passing an unprecedented $15 minimum-wage law this week, Seattle Mayor Ed Murray and the City Council promised the city it will be a positive economic experiment. That’s a big claim, with thousands of businesses at stake, not to mention tens of thousands of jobs.

Addressing the wealth gap in America is a critical issue. Raising the minimum wage is a strategy. Congress should raise the federal minimum wage to $10.10. But more important is universal access to high-quality education and job training.

In Seattle’s minimum-wage debate, the case was made that the local wage floor should rise. Elected officials settled on $15 — an arbitrary number picked by a group of particularly noisy activists. A good case also was made for a lower number.

The new law includes some concessions, agreed to by Murray’s advisory task force, although some members since have expressed disgruntlement. The process at least makes the new minimum wage slightly more palatable to businesses that will be paying it.

The council has yet to offer a plan to cushion the blow for its contractors in the nonprofit and human-services community. That plan must emerge quickly, because a seven-year phase-in for most nonprofits begins next April. Without a plan, nonprofits would have to make an untenable choice between their employees and their mission of serving the poor and people with disabilities.

Despite rosy rhetoric out of City Hall, the new minimum wage is a massive experiment that, in reality, goes far beyond $15. By 2025, Seattle’s inflation-adjusted minimum wage is predicted to be $18, more than $6 above what would be the inflation-adjusted statewide minimum wage. That gap sends a distinct message to fragile and low-margin businesses: hello, Renton.

Experiments should be adjusted as data comes in. Seattle’s leadership must promise the law is not etched in stone.

If the most dire predictions are realized, the City Council must revisit assumptions it used in passing the highest minimum wage in the country, and reopen the law.